Species appropriate nutrition means that a creature should eat what is has always eaten… Its historical, evolutionary diet. Shouldn’t this apply to humans as well as to Goldfish or Lions?
Scientists have only recently confirmed that the Giant Panda eats meat. Sounds odd that it took them so long to confirm that, but no one ever caught it live or on camera until 2011. Now we know that the correct species appropriate nutrition for Pandas should occasionally include meat with their ever-present bamboo.
What is the species appropriate nutrition for cats and dogs?
My cats prefer foods made with chicken, turkey, seafood and rabbit, rather than red meats such as beef or lamb. It suddenly occurred to me why.
Since cats are accustomed to eating birds, fish and rabbits in “the wild”, but seldom get red meat, their tastes tell them to eat their ancestral foods too. So they prefer poultry, fish and rabbit over beef and venison!
Makes sense, doesn’t it? They can hunt but they can’t catch large red meat mammals. 
Dogs of course are notorious for eating almost anything. Their natural diet is meat based, but they will eat vegetables, fruits and some plants. Neither dogs nor cats eat grains however, unless they are fully fermented by digestive enzymes found in the stomach of their prey.
If you are not feeding a “bones and raw food” diet (B.A.R.F. diet) to your dog, or freeze-dried raw prepared food, then canned grain-free food is best.
Neither dogs or cats are suited to dry kibble. Most kibble is grain-based, and the “meat” included is often more akin to feathers, beaks and bones. Many pets suffer from kidney ailments which I believe can be profoundly helped by eliminating dry food and feeding wet foods. (That doesn’t mean putting “gravy” on top of the kibble!) For a cost-saving tip, you’ll find that grain-free canned DOG food is often exactly the same as grain-free canned CAT food. But it comes in larger cans and is cheaper per serving.
What should humans eat?
In a Human-specific diet we hunted and ate the organs and fats from our prey as well as the less desirable muscle meat we mostly eat now. We gathered the plants, eggs, nuts and fruits we found along our traveling route. (Fruits would not usually have been plentiful, depending on the season, the latitude, and what other animals and insects found it first!)
Variety is the cornerstone of a Human diet, but we never fed on mass amounts of grains or sugars. We also never milked wild animals.
No matter who or what you wish to feed, consider the correct, appropriate diet for that creature. A little research into the Diet For Human Beings (here’s more info on the Diet and my DVD) could pay off for your health future. Or the diet for your favorite parrot or guinea pig too…
